UV curing is a photochemical process in which high-intensity ultraviolet light is used to instantly cure or “dry” inks, coatings or adhesives. Since its introduction, UV curing has been widely adopted in many industries including automotive, telecommunications, electronics, graphic arts, converting and metal, glass and plastic decorating. Popularity of UV curing has been increasing steadily owing to its many advantages over traditional drying methods.
Using light instead of heat, the UV curing process is based on a photochemical reaction. Liquid monomers and oligomers are mixed with a small percent of photoinitiators, and then exposed to UV energy. In a few seconds, the products—inks, coatings or adhesives instantly harden.
In recent years, pathogen reduction using riboflavin and UV light has been developed to inactivate infectious pathogens in blood ready for transfusion. This method reduces the infectious levels of disease-causing agents that may be found in donated blood components, while still maintaining good quality blood components for transfusion.
The development of pathogen inactivation/reduction technologies for blood products has been an ongoing effort in the field of transfusion medicine. The riboflavin and UV light method for pathogen reduction of platelets and plasma has been accepted in many countries throughout Europe. This same process is currently in development for the treatment of whole blood, resulting in pathogen reduction of the three components (RBCs, platelets and plasma). The application in United States and other countries will follow soon with regulatory issues being resolved.
In the applications listed above, precise control of UV illumination dose can be critical. A simple color change film indicating an exposure and/or measuring dose of the exposure of long wavelength UV can be very useful.
Lewis et al. (U.S. Pat. No. 4,734,355 and U.S. Pat. No. 4,970,137) have disclosed a type of radiochromic film which is sensitive to ionizing radiation. Upon radiation, a crystalline diacetylene undergoes solid state polymerization and forms colored polymer from colorless monomers. This type of film is particular sensitive to short wavelength UV, known as UVC with wavelength between 200 and 280 nm. The particular film is found to be less sensitive to the radiation of UV of long wavelength between 280 and 400 nm.
It is the objective of this invention to develop a film that has sensitivity to long wavelength UV to the extent required by the particular applications.
It is further the objective of this invention to develop a long wavelength UV indicator and/or dosimeter based on the film that indicates an exposure and/or measuring dose of long wavelength UV.